1. Field of the Invention
The present general inventive concept relates to an indirect transfer type image forming apparatus.
2. Description of the Related Art
Electrophotographic image forming apparatuses print an image by scanning an optical beam using an optical scanning unit, forming an electrostatic latent image on a photoconductive drum, developing the electrostatic latent image using toner, transferring the developed image onto a printing medium, and fixing the transferred image on the printing medium.
There are two types of electrophotographic image forming apparatuses: ones that directly transfer an image developed on a photoconductor onto a sheet of paper and fix the transferred image thereon, and ones that transfer an image developed on a photoconductor onto an intermediate transfer unit, overlap the transferred image with another image, transfer the overlapping image onto a sheet of paper, and fix the transferred image thereon.
The latter electrophotographic image forming apparatuses are classified as direct transfer type electrophotographic image forming apparatuses and indirect transfer type electrophotographic image forming apparatuses. When an image developed on a photoconductor is transferred onto an intermediate transfer unit, the former apparatuses simultaneously perform a pressure transfer and a magnetic field transfer since the photoconductor and a transfer roller are pressed against each other. The latter apparatuses perform the magnetic field transfer when the developed image is transferred onto the intermediate transfer unit since the photoconductor and the transfer roller are spaced apart from each other.
The indirect transfer type electrophotographic image forming apparatuses sequentially transfer color images onto the intermediate transfer unit, which increases a toner layer. Thus, it is necessary to sequentially increase voltages applied to a transfer roller for efficient transfer control.